The year is drawing to a close, the temperature has dropped and the oysters have now stopped growing, time for them to bed down and wait for the return of spring. So the question becomes how has the trial progressed through the year and what, if any, conclusions can be drawn?
In regard to the weather, in this part of Scotland it has been an odd year. The spring was very cold and wet, on series of days in May the water temperature on site was actually colder than December. This was followed by a wet and cool early summer. This undoubtedly held back our oysters and we observed, along with other growers in the area, very poor early season growth. The temperature then picked up a touch and we had a drier spell that was followed by an ‘Indian Summer’ helping to keep temperature up into late October. As a consequence we eventually observed a growth event and the oysters did well over the rest of the year.
We have two types of oyster, Pacific oyster (Rock oyster – Crassostrea gigas) and Native oyster (European Flat oyster – Ostrea edulis), on our trial site and the first observation that can be made is that both have grown successfully this year which has been very encouraging as this was one of the key goals of the trial.
The Pacifics have grown very well, they have put on a lot of shell and are now starting to develop cup as they start to gain weight. As can be seen the shells are very clean and have lovely colouring ranging for pearl white to vivid purple and combinations of both. We are pleased to see that the rumbling effect caused by the culture equipment is resulting in the shells developing a very pleasing teardrop shape.
The European Flat oysters (or Natives) after a poor start to the year have also grown well. The data we have collected seems to show that the Natives are very consistent and steady in their growth once they get going, as opposed to the Pacifics which are a bit more erractic. We are delighted and encouraged that the Natives appear to grow well and as can be seen in the following image, the shells are very aesthetically pleasing.
They tend to be round with length and diameter being almost identical and have a beautiful pearl white colour, with a tinge of pinky red present in many. We are surrounded by mountains of red Torridonian sandstone which is reflected in the deep red colour of the sand and we can not help but wonder if the Natives are absorbing these same minerals into their shells. Wishful thinking? Perhaps but the Natives are definitely a good looking oyster!
In general the Pacific oysters have outperformed the Native oysters but this is to be expected as it is widely known that the Pacifics have a more aggressive growth rate than the Native oyster and this is the reason it is the aquaculture oyster of choice in Europe and much of the world. It is also interesting to note growth spread amongst the oysters, which is most observable with the Pacific oysters. Just like people it would seem that oysters grow at different rates.
In summary an interesting year, despite a very poor spring and early summer a return to better conditions resulted in good growth. We were able to demonstrate that cultivation using our chosen method is feasible, if the oysters can grow in as bad a year as this then the signs are good.
So is the trial a success? The conclusion has to be that it is too early to say but we are encouraged enough to take the next step and make an application for a small production site. Using the lessons we have learned this year we are going to tweak our approach slightly in terms of site layout and we are also going to focus on growing the European Flat oysters.